Losing connection with open loop steppers.

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garageng1neer
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Losing connection with open loop steppers.

Post by garageng1neer »

I have done all the research possible to find this problem. I did not see anything in the history of the chat board. The closest I have found to answering the problem was finding Franco on YouTube. He posted "Centroid Acorn CNC:Step Rate and Driver Frequency Interactions". Most information seems to be out there about closed loop steppers. (I get it, closed loop makes sure that things get where they are directed.)

The Issue:
Somewhere, I am losing connection from the acorn to my stepper motors somewhere. I'll home the machine and none of the axis will move. After homing the machine the only axis that will move is the Z in the (-) direction, but the DRO on the computer screen says that whichever axis I am moving, that axis is moving. Acorn seems to think everything is working fine, but it isn't.

Setup:
I have made various decisions out of economy and (maybe not knowing better). I originally found complete assembly ball screws on amazon built by RATTMMOTOR with the stepper Motor already mounted (I attached the PDF of the Stepper info) on the assembly they used. Since they used open loop steppers, I chose the StepperOnline DM556T Stepper Drivers. (I figure most open loop steppers are pretty good any more at not losing steps unless you really push them.)
StepperInfo.pdf
(33.01 KiB) Downloaded 1 time

Most machines that I saw did not have the Z travel that I needed, so I opted to build my machine with 2-400mm ball screw assemblies to get the height I wanted. Most machines I see have double screws on the Y-axis (and I get the whole racking with Y-axis movement). I wanted to limit the amount of movement and make the spindle head as stable as possible, so the Y-axis only moves the table and the Z only moves the X gantry up and down. This is getting off the subject of my problem, but wanted to explain my thinking with this design. I have connected the DM556T to the acorn according to the schematic for the open loop driver. As in the schematic I've included, it only shows 1 drive connected to the DB25 connector. I have the Y-axis connected to PUL to pin 4, DIR to pin 5. Z1 & Z2 axis share a connection PUL to pin 6 and DIR to pin 7. That shared connection splits and goes to separate stepper drivers.
leadshineDMSchem.pdf
(152.99 KiB) Downloaded 2 times
I purchased the Acorn board last year. I had the stepper drivers and was able to do a bench test shortly after it arrived. At the time, I only had 1 Z-axis connected, but everything worked as it was suppose to, all the axis moved back and forth, the steppers sounded smooth and everything was working fine.

20240420_091905.jpg
Problem:
Having a regular job, only working on this on weekends I had to disassemble the bench test, and reassemble in a control panel over the next few months. Apparently when I did re-assemble into a control panel, I screwed something up. Up to this point, I'll start Acorn12, I'll press the reset on the virtual control, then Cycle Start to home the Machine. Sometimes the axes will move while zeroing (lately not so much, as of now none of them move), I'll touch the home sensor until all are Zeroed. Then I will JOG some of the axis & it will move, but when I go to move another axis it won't, then I go back to the original axis and it will no longer move (For example: I will move the x-axis, it will move just fine (+) and (-). I'll move the Z-axis. (it will show that it is moving on the DRO, but in reality it is not moving.) I will go back to the X-axis and then it no longer works. Now, none of the axes will move while homing the machine, and when I go to jog an axis, only the Z will move in the (-) direction. Sometimes, it will be only 1 Z axis that moves and it is usually only in the (-) direction.


Currently, Machine Settings:
While I have checked the wiring multiple times (I don't think that is the problem, but it still might).
1.The stepper drivers are set to 3200 step/rev. Current is set to 2.7A (Motors are rated at 2.8A)
2.The Acorn is set to 3200 step/rev.
3.The DM556 stepper driver has minimum pulse of 2.5 microSec. I set Acorn's Parameter 968 to 5, which corresponds to 240000Hz (it is the closest I could find to the pulse rate of the DM556T).
4.The data cable from the Acorn DB25 to the DM556T is a shielded cable with the shielding wire grounded to the chassis of the control panel.
5.Included the zip file from the Acorn.

At one point, while trying to diagnose the prob, I used and Arduino. One by one, connecting the Arduino to each axis. The code written on the Arduino would move each axis. They sounded good and ran smoothly in both direction. So this leads me back to the Acorn.

Obviously, I have tried to include as much information as possible. I am starting to wonder if I need to upgrade to steppers to closed loops. I have spent so much time trying to get this to work and I am getting so very frustrated. If I have to fix the problem, I will. I just feel that is going to set me back. I just think there is a setting that I have screwed up somewhere.

I appreciate any help to resolve this because at this point I want to destroy this with sledgehammer, and I would really like not to have to start over. Thank you.

P.S. Not sure why all pic loaded 90 deg off. This is my 1st time posting anywhere.
Attachments
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Gary Campbell
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Re: Losing connection with open loop steppers.

Post by Gary Campbell »

What voltage is the power supply for the drives?

Set your step pulse to 100khtz. Those drives are not 200k
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garageng1neer
Posts: 4
Joined: Fri Mar 29, 2024 5:46 pm
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Re: Losing connection with open loop steppers.

Post by garageng1neer »

I am running 24V from a Rhino Power supply to power the drivers, but I have a 5V from a separate Rhino power supply that is (+) on PUL and DIR. I will try the 100 kHz. Thank you.
Gary Campbell
Posts: 2199
Joined: Sat Nov 18, 2017 2:32 pm
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CNC Control System Serial Number: Acorn 238
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CNC12: Yes
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Location: Bergland, MI, USA
Contact:

Re: Losing connection with open loop steppers.

Post by Gary Campbell »

You should use 48vdc with those drives
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garageng1neer
Posts: 4
Joined: Fri Mar 29, 2024 5:46 pm
Acorn CNC Controller: Yes
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AcornSix CNC Controller: No
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Hickory CNC Controller: No
Oak CNC controller: No
CNC Control System Serial Number: 98F07B920C80-0207236969
DC3IOB: No
CNC12: Yes
CNC11: No
CPU10 or CPU7: No

Re: Losing connection with open loop steppers.

Post by garageng1neer »

Ok, I've ordered a 48V DC power supply, it should be here in a day or so.

In the meantime, I have an observation that I made the other day though. I changed the setting to what you suggested of 100,000 Hz. When I homed the machine none of the axes moved, so I triggered the Home Limit switches. Then I went to MPG screen, I tried jogging the X-axis, the Y-axis in either direction...I got no movement. I tried to jog the Z-axis in (+) direction I got nothing. Then I did the Z-axis (-), it moved down. I went back and checked the X and Y axes. The X started moving in both (+) & (-) directions, the Y would only move in the (-) direction.

I then hit the Z in the (+) direction then everything stopped. It is almost like the Z-axis is acting like a switch turning on and off the X & Y but only kind of. Would this be some sort of setting on the acorn board? I just find the very strange.

I appreciate your input, thank you.
ShawnM
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Re: Losing connection with open loop steppers.

Post by ShawnM »

Please post a CURRENT report from the machine. Anytime you have issues AND you have made machine changes you must post a new report so we can see your current settings. We can see how the machine is setup and look at your error log as to what the issue might be.
garageng1neer
Posts: 4
Joined: Fri Mar 29, 2024 5:46 pm
Acorn CNC Controller: Yes
Plasma CNC Controller: No
AcornSix CNC Controller: No
Allin1DC CNC Controller: No
Hickory CNC Controller: No
Oak CNC controller: No
CNC Control System Serial Number: 98F07B920C80-0207236969
DC3IOB: No
CNC12: Yes
CNC11: No
CPU10 or CPU7: No

Re: Losing connection with open loop steppers.

Post by garageng1neer »

Sorry, Here is the latest zip file from my machine. I took it after I was noticing the strange be behavior with the Z-axis.
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